Method of assembling a flat electrical cable

ABSTRACT

A flat electrical cable and a modular rotary anvil for assembling a flat electrical cable wherein the flat cable includes an upper and lower layer. The upper layer has ribs protruding along its length that are substantially parallel to one another, and continuous substantially parallel and adjacent seams formed therebetween. Conductors are placed between the upper and lower layers adjacent the seams. The present invention may have upper and lower polyester layers having copper conductors therebetween and the seams ultrasonically welded in order to provide a flat electrical cable for various applications such as incorporation in an automobile clockspring. The modular rotary anvil includes multiple removable and interchangeable segments or inserts which provide the ability to impart a smooth or knurled textured surface pattern to the work-piece. piece. Other inserts include cutting inserts which provide for a seam on the work-piece while a the same time cuts the work-piece along a seam.

CROSS REFERENCE TO RELATED DOCUMENT

The present application is a division of application Ser. No.09/454,333, filed Dec. 3, 1999, now U.S. Pat. No. 6,841,735, which is aCIP of application Ser. No. 08/627,136, filed Apr. 3, 1996, now U.S.Pat. No. 6,026,563 the subject matter of each of which is hereinincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to flat cable and an apparatus for makingflat cable. The invention more particularly concerns flat electricalcable with exposed conductors without adhesive residue and a modularrotary anvil which is used to manufacture the flat electrical cable.

2. Discussion of the Background

Flat electrical cables are well known in the art having conductorssandwiched between two insulating layers. Flat conductor cable is knownin the art having an upper insulator layer having an adhesive adhered toa first side of the upper layer and a lower layer of insulating materialhaving an adhesive adhered to a first side of the lower layer. Aconductor or strands of conductors are placed between the upper andlower insulator layers and all three layers are secured together by theadhesive. However, use of adhesive to bond the layers is disadvantageousin that upon heating of the adhesive, the conductors may float in thefree flowing adhesive causing the spacing between the conductors to beinconsistent and non-parallel. Upon drying and attempted attachment ofthe flat cable to a component, the improperly placed conductor may notalign with the conductive leads of the component the cable is to beattached and, thus, the flat cable is unusable and must be discarded.Further, when the cable is stripped to expose the conductors forconnection of the cable to a component, the conductors have an adhesiveresidue thereon which inhibits the conductive properties of theconductor. Also, if any scrap material of the insulator layers isproduced, the scrap may not be recycled due to the presence of theadhesive on the insulator layer.

Other bonding techniques are known in the art for bonding multiplelayers such as ultrasonic welding. Generally ultrasonic welding has beenused for spot welding with thermoplastic materials using either a plungemode or a shear mode. Therefore, the known methods of weldingthermoplastic materials using ultrasonics did not provide for acontinuous welded seam where the seam has great pull strength. In thearea of electrical cables, seams of great pull strength are required andthe previously known welding techniques are not sufficient.

The ultrasonic welding apparatus includes an ultrasonic welding machine1, as shown in FIGS. 14 and 15. The ultrasonic welding machine 1includes inner and outer brackets 2 and 3, the anvil frame 4, the horn5, the pattern roller or rotary anvil 6 mounted to the anvil frame 4, achain 7 to rotate the rotary anvil 6. However, other methods of rotatingthe rotary anvil 6 can be used. Socket head cap screws 8 attach theouter bracket 3 to the anvil frame 4. The rotary anvil 6 is mounted inopposition to the horn 5. As shown, in FIGS. 14 and 15, the work-piece(not shown) is fed into and through the gap 9 present between the horn 5and the rotary anvil 6. As the horn 5 plunges or shears against thework-piece, the rotary anvil 6 remains rigid in the opposing directionof the force and subsequent impacting of the work-piece by the horn 5,thus reacting the forces generated by the process. In this example, asshown in FIGS. 14 and 15, the horn 5 does not rotate. As such, nopattern is formed on the side of the work-piece facing the horn 5, ifthe surface of the horn is flat and smooth. As the work-piece passesthrough the gap 9 between the horn 5 and the rotary anvil 6, the rotaryanvil 6 rotates. Thus, a pattern can be imprinted on the surface of thework-piece. Such a method of manufacture requires that a unique anvil becreated and inventoried for every type of and size of pattern desired tobe formed on the work-piece.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide a flatelectrical cable which is bonded without use of adhesives and providesfor a continuous seam.

It is another object of the invention to provide a flat electrical cablethat is light in weight.

It is still another object of the invention to provide a flat electricalcable that has a high natural frequency.

It is a further object of the invention to reduce the number of toolsrequired to be kept in inventory for producing the flat electricalcable.

It is another object of the invention to increase the variety of toolsets being run at the same time.

It is an additional object of the invention to support flexiblemanufacturing of flat electrical cable.

It is another object of the invention to provide a method of assemblinga flat cable by bonding without using adhesives and to provide thecapability of forming a continuous seam and other types of seams.

It is a further object of the present invention to provide a flat cablehaving exposed conductors without an adhesive residue.

It is another object of the present invention to provide a flatelectrical cable which operates quietly during use in a clockspring.

It is a further object of the invention to provide a durable flatelectrical cable.

It is still another object of the invention to provide a flat electricalcable which carries a large amount of current for a long period of time.

It is still a further object of the invention to provide a flatelectrical cable which conveys many functions such as pulse heating to asteering wheel.

It is still another object of the invention to provide a flat cablehaving multiple types of conductors, conductor groups, or opticalfibers.

It is yet another object of the invention to provide for a low cost flatelectrical cable.

A principal object of this invention is to provide a flat electricalcable comprising an upper insulator layer, a lower insulator layerconnected to the upper layer, a lower insulator layer connected to theupper layer along substantially continuous parallel spaced-apart seamsand an intermediate layer comprised of individual strands of conductorswhich lie adjacent and substantially parallel to the seams and theconductors do not have an adhesive residue thereon. The upper layer mayinclude a plurality of raised surfaces running parallel to each otheralong the length of the flat cable. The lower layer may be substantiallyplanar and include a pattern formed on the majority of the surface ofthe lower layer. Seams positioned between adjacent conductors have atextured surface pattern, and seams positioned along edges of the flatelectrical cable have a substantially smooth surface pattern. The upperand lower insulator layers may be polyester. The conductors may becopper. The seams may be ultrasonically welded. The conductors may beexposed at an end portion of the flat cable beyond the upper and lowerinsulator layers. The cable may include a continuous seam except for anonbonded area where the upper and lower insulator layers are notconnected. The cable may include a continuous seam except for anonbonded area where the upper and lower insulator layers includewindows that expose the conductors.

In still another embodiment of the invention, a flat cable is providedcomprising an upper insulator layer, a lower insulator layer, and anintermediate layer. The lower insulator layer connected to the upperinsulator layer along substantially continuous parallel spaced apartseams. The intermediate layer comprised of conductor groups which lieadjacent and substantially parallel to the seams. Furthermore, theconductor groups do not have an adhesive residue on their outer surface.

In another embodiment of the invention, a flat electrical cable isprovided comprising an upper layer of polyester having a ribbed surface,a lower layer of polyester connected to the upper layer alongsubstantially continuous parallel spaced-apart ultrasonically bondedseams and individual strands of copper conductors lying substantiallyparallel and adjacent to the seams between the upper and lower layers.The lower layer may have a pattern along the majority of its exposedsurface. Seams positioned between adjacent conductors have a texturedsurface pattern, and seams positioned along edges of the flat electricalcable have a substantially smooth surface pattern.

In another embodiment of the invention, a clockspring is provided forelectrically connecting an airbag in a steering wheel of a vehiclethrough a steering column to crash sensors, the clockspring comprising ahousing having an inner chamber and a flat electrical cable including anupper insulator layer, a lower insulator layer connected to the upperlayer along substantially continuous parallel spaced-apart seams and anintermediate layer comprised of individual strands of conductors whichlie adjacent and substantially parallel to the seams and the conductorsdo not have an adhesive residue thereon, the flat electrical cable beingmounted in the chamber of the clockspring. Seams positioned betweenadjacent conductors have a textured surface pattern, and seamspositioned along edges of the flat electrical cable may have asubstantially smooth surface pattern.

In a further embodiment of the invention, a modular rotary anvil for anultrasonic welding machine is provided comprising a first end segment, asecond end segment, and a at least one insert having a first side and asecond side, each of the first side and the second side configured toattach to at least one of other inserts, the first end segment, and thesecond end segment. The first end segment and the second end segmentconfigured to attach to the ultrasonic welding machine.

In another embodiment the invention takes the form of a method ofassembling a flat electrical cable. The steps of producing the flatelectrical cable include simultaneously feeding an upper and lower layerof insulating material and an intermediate layer of conductors between ahorn and a modular rotary anvil, and the next step being ultrasonicallybonding the upper and lower layers together along a seam substantiallyadjacent the conductors.

In still yet another embodiment the invention takes the form of a methodof assembling a clockspring. The steps of producing the clockspringinclude inserting a flat cable into a clockspring housing, where theflat cable is made pursuant to the method steps recited in the paragraphabove.

These and other features of the invention are set forth below in thefollowing detailed description of the presently preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a perspective view of the flat cable of the present invention;

FIG. 2 is a side-elevation view of the preferred apparatus for bondingof the flat cable;

FIG. 3 is an enlarged view of the bonding area of FIG. 2;

FIG. 4 is a side-elevation view of the assembly machinery and process ofthe present invention;

FIG. 5 is a perspective view of an alternate embodiment of the flatcable of the present invention showing the flat electrical cable afterthe end portion has been stripped to expose the conductors;

FIG. 6 is an enlarged view of the bonding area of FIG. 2 where a modularrotary anvil is shown being used with a horn moving in a plungingaction;

FIG. 7 is a perspective view of an alternate embodiment of the flatcable of the invention which was formed with the use of the modularrotary anvil;

FIG. 8A is a front view of one embodiment of the modular rotary anvil;

FIG. 8B is an expanded detailed view of FIG. 8A;

FIG. 9A is a front view of another embodiment of the modular rotaryanvil;

FIG. 9B is an expanded detailed view of FIG. 9A;

FIGS. 10A and 10B are a side view and a front view of a large bracketinsert from FIG. 8A;

FIGS. 11A and 11B are a side view and a front view of a small bracketinsert from FIG. 8A;

FIGS. 12A and 12B are a side view and a front view of one knurled insertfrom FIG. 8A;

FIGS. 13A and 13B are a side view and a front view of one smooth seaminsert from FIG. 8A;

FIG. 14 is an exploded side view of a related ultrasonic weldingmachine;

FIG. 15 is a side view of an assembled, related, ultrasonic weldingmachine of FIG. 14;

FIG. 16 is a perspective view of another alternate embodiment of theflat cable of the invention which was formed with the use of the modularrotary anvil;

FIG. 17 is an expanded view of a portion of an alternate knurl pattern;

FIG. 18 is an end view of a single conductor;

FIG. 19 is an end view of dual or tandem conductors;

FIG. 20 is an end view of dual stacked conductors;

FIG. 21 is an end view of tripled stacked conductors;

FIG. 22 is an end view of a wire rope conductor;

FIG. 23 is an end view of a compressed wire rope conductor;

FIG. 24 is an exploded, perspective view of a single flat conductorassembled with upper and lower insulation layers;

FIG. 25 is an exploded, perspective view of a dual tandem conductorgroup assembled with upper and lower insulation layers;

FIG. 26 is an exploded, perspective view of a triple stacked conductorgroup assembled with upper and lower insulation layers;

FIG. 27 is an exploded, perspective view of a dual stacked conductorgroup assembled with upper and lower insulation layers; and

FIG. 28 is an exploded, perspective view of a wire rope conductor groupassembled with upper and lower insulation layers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views, and moreparticularly to FIG. 1 thereof which shows a finished flat conductorcable 10 of a preferred embodiment of the present invention. The flatcable 10 has an upper layer 20 and a lower layer 30 formed of aninsulating material. In a preferred embodiment, polyester insulator isused, such as that having a thickness of 0.001 inches. However, thickerinsulator materials may be used to provide stronger bonds, such as wherethe seams are narrow. Intermediate the upper and lower layers 20, 30 areconductors 40. The conductors 40 are made of individual strands ofmetallic material which lie substantially parallel to one and anotheralong the length of the cable 10. In a preferred embodiment, theconductors are formed of annealed copper having a dead soft hardnessrating. However, any other conductor may be used such as copper cladsteel. Furthermore, the conductor can be replaced with a fiber opticcable. The conductors 40 are separated by seams 50. The seams 50 areformed by the continuous bonding between the upper layer 20 and thelower insulator layer 30. A plurality of parallel spaced-apart seams 50run continuously along the length of the cable 10. In a preferredembodiment, the spacing between the plurality of conductors 40 comprisesthe seams 50. In other words, the width of each seam 50 approximatelyequals the space between the adjacent conductors 40. In such aconstruction, the conductors 40 are trapped in a pocket or encapsulatedbetween the seams 50 and the upper and lower insulator layers 20, 30 toavoid any shorting between the parallel strands of conductors 40. In apreferred embodiment, the seams 50 are ultrasonically bonded, which willbe discussed further below.

The cable 10 includes a raised surface 25 or ribs above the conductors40 on the upper layer 20 of the insulator. The raised surface 25provides for a ribbed texture along the upper surface 20 of the cable 10and reduces the surface area of the upper layer 20 so that less frictionis created when the upper layer 20 rubs against another surface. In anembodiment where the flat cable 10 is wound in a spool, the noise of thesurface of the upper layer 20 of the flat cable 10 rubbing against thelower layer 30 will be reduced due to the ribs 25. In addition, inanother embodiment, the lower layer 30 of the flat cable 10 has apattern 35 adhered thereto. The pattern 35 acts to reduce the surfacearea of the most extraneous portions of the lower layer 30 in order tofurther reduce friction and noise of the lower layer 30 rubbing againstanother surface.

In the preferred method of assembling the flat cable 10, the bonding ofthe upper and lower layers 20, 30 occurs only at the plurality of seams50 and no bonding of the upper layer 20 or lower layer 30 occurs to theconductors 40. In such an arrangement, the conductors 40 are bounded oneach side by the seams 50 but are loose in the compartment formed by theupper and lower layers 20, 30 which are not bonded in the area along thelength of the conductor 40. This arrangement provides an advantage inthat when the end of the cable 10 is stripped and the conductors 40 areexposed, the exposure operation is simplified in that there is nobonding between the conductors 40 and the upper or lower layers 20, 30.Therefore, there is no residue on the conductors 40 and cleaning of theconductors is not required in order to provide the desired level ofconductivity. An edge 15 of the flat cable 10 is also bonded and has acontinuous seam such as provided by an ultrasonic weld. This edge 15 maybe provided by cutting the flat cable 10 via slitting station 89 shownin FIG. 4. The edge 15 produced by cutting is a smooth edge or surface.The smooth surface of the edge 15 results in a flat electrical cablewhich provides for quiet operation during use in a clockspring, eventhough the edge 15 contacts sound damping material of the clockspringhousing.

In the preferred embodiment, the seam 50 is continuous and runs alongthe entire length of the cable 10. The preferred use of the flatelectrical cable 10 of the present invention is in an automobileclockspring which provides for the electrical connection of the airbagof an automobile steering wheel through the steering column tostationary crash sensors in the automobile. In such clocksprings, theflat ribbon cable is wound around an inner chamber of the clockspringhousing and generally has a length of approximately two feet. In theprocess described below, the flat cable is formed continuously in spoolsof over one-thousand feet or any desired length. The spool of cable islater cut to two feet lengths and the ends of the two feet lengths arestripped. In the preferred embodiment of the invention, the overalllength of the seams will be equal to the length of the entire spool ofcable, as the seams 50 are continuous.

In an alternate embodiment, the seam may be noncontinuous at theseparation areas of the cable 10. Thus, the majority of the length ofthe cable 10 has a continuous seam 50 except at the end of that portionof the cable having a desired length to be used and attached to acomponent. For example, at two feet intervals along the length of thecable 10 a narrow nonbonded separation area may be formed. The nonbondedareas are located at the point along the cable where it is intended thatthe flat cable will be cut or separated. A nonbonded area will be formedevery two feet of the cable so that the end portions of the two footlengths of the flat cable 10 will have small areas, for example, oneinch lengths, which are nonbonded. In this way, the ends of the cablemay be easily processed in order to expose the conductors 50. Having thenonbonded areas allows for the top and bottom layers to easily beclipped or cut to expose the conductors 40. In the previously mentionedembodiment having completely continuous seams, the desired lengths ofthe flat cable must be inserted in a grinding or buffing machine inorder to remove the layers of insulation and expose the conductors orcut the insulator layers from between the conductors. The method offorming the nonbonded areas at specific intervals along cable will bediscussed further below.

An alternate embodiment of the present invention may be provided havingmultiple layers of insulating material and conductors therebetween.Additional layers may include ground wires or a ground plane or a drainwire or additional layers to limit cross talk.

The method of assembling the flat cable of the present invention is bestunderstood with reference to FIGS. 2–7. One specific bonding processwill be discussed with reference to FIGS. 2, 3 and 6 and the overallprocess with reference to FIG. 4. Turning to FIG. 2, a rotary horn 60 isshown having weld surface 65. Adjacent the rotary horn 60 is rotaryanvil 70. The rotary anvil 70 rotates about axis 71 and rotary horn 60rotates about axis 61. The rotary horn 60 provides for the ultrasonicbonding of the flat cable which is inserted between the rotary horn 60and the rotary anvil 70. In a preferred embodiment, a full wave rotatinghorn of titanium is used in order to provide for a weld surface 65 ofgreater than one inch. In a preferred embodiment, the weld surface 65 isthree inches wide. The three inch wide weld surface 65 is preferred sothat the maximum footage of flat cable 10 may be produced. Although inthe preferred embodiment of the end use of the cable 10 widths areapproximately one-half inch, the three inches wide weld surface 65allows for the simultaneous assembly of six cables side-by-side, to beseparated later. The three inch weld surface 65 provides for the maximumwidth without sacrificing a uniform amplitude level of the rotary horn60 so that the ultrasonic bond strength is maintained. In oneembodiment, the full wave horn 60 provides for ultrasonic bonding via ashear mode or in the horizontal direction of arrow 67. The use of thefull wave horn having a shear mode provides for continuous welding toform a continuous seam 50 of the flat cable 10. As is known in theultrasonic bonding art, the rotary horn 60 is attached to a converterand a booster which generates a voltage which creates a wave whichpasses through the rotary horn 60 and causes the rotary horn 60 tooscillate or vibrate in the direction of arrow 67. In one embodiment,the horn will vibrate at approximately 20 kHz. However, the horn can bevibrated at frequencies in the range of 30 or 40 kHz. Furthermore, therotary horn 60 can be vibrated in the plunge mode, as is describedbelow.

Turning to FIG. 3, an enlarged view of the FIG. 2 shows the bonding areabetween the weld surface 65 of the rotary horn 60 and the rotary anvil70. The rotary anvil 70 includes a plurality of copper locating grooves72 and interspersed between the grooves 72 are protrusions 74. The flatcable is fed between the weld surface 65 of the rotary horn 60 and therotary anvil 70 at gap 68 so that the upper insulator layer 20 isadjacent the rotary anvil 70 and the lower layer 30 is adjacent therotary horn 60. The grooves 72 and protrusions 74 of the rotary anvil 70are designed and oriented according to the specific arrangement andspacing of conductors desired in the flat cable. In the embodiment shownin FIG. 3, the rotary anvil 70 has been designed to form a flat cablehaving six conductors as can be seen by the group of six grooves 72. Therotary horn 70 is designed so that a batch of flat cables are formedsimultaneously side-by-side which may be separated later during theassembly process. The broad protrusion 75 provides for a broad space inorder to allow for the separation of individual flat cables. In apreferred embodiment, the anvil and weld surface 65 of the rotary horn60 are designed to make six individual cables simultaneouslyside-by-side, each having six conductors. In the present embodiment, theentire bonding surface between the weld surface 65 of the rotary hornand the rotary anvil 70 is three inches wide. Each individual flat cableis approximately half of an inch wide and therefore, six individualcables can be formed simultaneously and later split in order to form theindividual flat cables. Therefore, in the preferred embodiment, therotary anvil 70 will have five wide protrusion areas 75 in order to formsix separate areas having six grooves 72 to form each individual flatcable having six conductors therein. The grooves 72 have a width justslightly larger than the width of the conductors being bonded within theflat cable. In the preferred embodiment, the width of the grooves 72 is0.045 inches. The spacing of the conductors is determined by the widthof the protrusion 74. In the preferred embodiment, the protrusions 74all have the same width of approximately 0.0338 inches. However, allthese dimensions may vary dependent on the overall design andrequirements of cable desired. In an embodiment, the rotary anvil 70 maybe interchangeable with other rotary anvils having different spacing ofthe grooves 72 and protrusions 74 to assemble a flat cable havingdifferently spaced conductors. In a preferred embodiment, as discussedbelow, the rotary anvil 70 takes the form of a modular rotary anvil 70 aas shown in FIG. 6, where multiple rotary anvils 70 are not required tobe on hand to produce flat cable having different spacing of thegrooves.

The upper and lower insulator layers having conductors arranged inbetween and spaced corresponding to the spacing of the protrusions 74 ofthe rotary anvil 70 are fed between the rotary anvil 70 and the rotaryhorn 60 where bonding of the assembly will occur. The height of the gap68 between the protrusions 74 and the weld surface 65 is slightly lessthan the combined height of the two layers of the insulator. Therefore,upon insertion of the upper and lower insulator layers between the weldsurface 65 of the rotary horn and the rotary anvil 70, the insulatorlayers are compressed between the protrusions 74 and the weld surface65. The conductors 40 of the flat cable 10 are spaced correspondingly tothe grooves 72. The conductors 40 fill the space in each groove 72 abovethe weld surface 65. The grooves 72 have a predetermined depth in orderto avoid the welding of the conductors to the upper and lower insulatorlayers 20, 30. As the depth of the grooves 72 increases, the amount oftension placed on the lower layer 30 of the flat cable against the weldsurface 65 is reduced so that welding does not occur between theconductor and the insulator layers 20, 30. In a preferred embodiment,the grooves 72 have a depth of 0.004 inches.

In one embodiment, the insulator layers 20, 30 and conductors 40 are fedthrough the gap 68 at a speed of approximately 4 inches per second. Thevibrating rotary horn 60 creates a frictional heat at the weld surface65. Bonding occurs at the points where the protrusions 74 compress theinsulator layers against the active weld surface 65. The compressiveforce between the protrusion 74 and the weld surface 65 cause thebonding between the upper and lower insulator layers to occur only atthis interface. The protrusions 74 also provide for the shape of upperinsulation layer 20 of the flat cable 10. The grooves 72 form the raisedarea 25 of the flat cable 10 and the protrusions 74 form the depressedseams 50. Further the weld surface 65 of the rotary horn 60 includes apattern which is burned into the lower layer 30 of the insulator. In oneembodiment, the pattern on the weld surface 65 is 90° knurl.

It can thus be understood that there is no bond between the upper andlower insulators at the groove area 72 in which the conductor islocated. Therefore, upon the process of exposing the conductors in orderto provide for attachment of the flat cable 10 to a component, theconductors 40 may be easily exposed because there is no insulatormaterial adhered to the conductors 40. Further, it can be understoodthat the present invention overcomes the prior art in that there is noadhesive bonded to the conductors in that the bonding of the presentinvention only occurs at the predetermined areas where the protrusions74 are located.

Turning to FIG. 4, the overall method of assembly of the flat cable 10may be understood. The operation starts on the right side where multipleconductor reels 81 are mounted. In one embodiment, copper is used asconductors and these copper reels are purchased from Torpedo WireCompany (Pittsfield, Pa.). The conductors are pulled off of theconductor reels 81 and fed through the wiping area 82 in order to bringthe conductors to the same plane and to clean the metallic conductorsand remove any residue which might reduce conductivity. The conductorsare then fed through the wire separation module 83. The conductor wiresare then fed through the conductor straightening module 84 which is aseries of grooved rollers that align the conductors. The conductors arethen aligned in their final orientation by the conductor guide 85. Theconductor guide 85 includes grooves which are spaced corresponding tothe grooves 72 of the rotary anvil 70. Because the present method doesnot use adhesives and such liquid adhesives are not present on theinsulator layers, the conductors remain positioned on the insulatorlayers according to the conductor guide 85. Further, the grooves 72 onthe rotary anvil 70 also act to maintain the spacing of the conductors40. The upper insulator reel 86 and lower insulator reel 87 includetension control means and are fed along with the conductor wires betweenthe rotary horn 60 and the rotary anvil 70. The rotary anvil 70 includesguides along its edges in order to align the upper and lower insulatormaterials and the array of conductor wires. In a preferred embodiment,the upper and lower insulator materials are a clear polyester purchasedfrom Plastic Suppliers, Inc. (Chicago Heights, Ill.).

The rotary horn 60 is controlled by the sonic controller and powersupply 88. In one embodiment, the power supply is an Amtech 920 MAadvanced high frequency constant amplitude power supply providing a 20KHz at 2,000 watts (Amtech, Inc., Milford, Conn.). In a preferredembodiment, the controller includes a speed control in order to increaseand decrease the speed of the assembly process. The power supply wouldalso include an encoder in order to reduce the power when the process isslowed. When the various reels feeding the process need to be exchanged,it is desirable to slow down the process so that the reels may bechanged more easily. The encoder and speed control features arecoordinated in order to allow for this process. In an alternateembodiment, the controller will include a continuous mode adjustmentwhich allows for the bonding to occur in a continuous mode or anoncontinuous mode and set the intervals at which the bonding willoccur. As discussed above, it may be desirable to provide for nonbondedareas at the ends of the desired lengths of the flat cable where it willbe separated. The continuous mode feature will provide for the “off”function of the ultrasonic welding for a preprogrammed amount of time sothat a specific distance of the flat cable may have a nonbonded area andthe automatic switching of the ultrasonic bonding back to an “on”position in which the continuous bonding is resumed. The controller in apreferred embodiment also includes an amplitude adjustment in order tovary the amplitude in order to control the bonding quality of the rotaryhorn. In a further alternative method of forming flat cable, insulatorlayers having windows at predetermined intervals may provide prestrippedareas in which the conductors are exposed even during bonding.

Adjacent the rotary horn 60 is a cooling mechanism in order to cool theweld surface 65 of the horn 60. Also adjacent the bonding area may be ameans of testing the presence and quality of the bond at the seams 50.In a preferred embodiment, a vision system may be used to test the seams50. As the polyester used as insulators in the preferred embodiment isclear and the rotary horn includes a pattern, the bonded seams are notclear. Thus, a vision system may be programmed to test the clarity ofthe patterned bonded seams 50 of the successfully welded flat cable 10.If the cable is not bonded, the seams will remain clear and light willpass through the seam 50 without distortion and the bond testing meansmay be programmed to shut down the assembly process. Such a system mayalso be programmed to test and record the bonded and nonbonded areas asdiscussed above in an alternate embodiment.

The bonded flat cable is then pulled through cable slitter 89 in orderto split the full widths of the cable into the desired widths of thesubgroups of usable flat cable. As discussed above, in a preferredembodiment, the flat ribbon cable is bonded in three inch wide segmentsand then separated into six, half inch wide cables having six conductorseach. The individually spliced flat cables then move through pullerrollers 90. The puller rollers 90 pull the insulator layers and theconductor wires through the entire assembly process. Finally, theindividual flat cables are received by take-up reels 91. The reels withthe flat ribbon cable may then be transported to the specific areaswhere the flat ribbon cable 10 is to be used and the flat ribbon cable10 would be cut to the desired lengths and have the ends processed inorder to expose the conductors for attachment to a component such as aclockspring. In an alternate embodiment, the assembly process may haveincorporated into it the cutting of the flat cable to the desired lengthand the process for exposing the conductors.

The stripping process may include the insertion of the end of the flatcable between a rotary grinding machine in order grind off the upper andlower insulator layers to leave the conductors exposed. The excess areabeyond the exposed conductors may then be trimmed so that bare exposedconductors protrude from the end of the flat cable so that they may bemounted to a component such as an electrical connector and solderedthereto. In an alternate method of stripping the cable ends, a pluralityof spaced, adjacent knife blades or punches may penetrate the insulatorlayers and pull the insulator layer from between and off of theconductors. The present invention provides for the flat cable having theconductors mounted between the insulator layers but not bonded to theinsulator layers which provides for an easier stripping process. Becausethe conductors are not bonded to the insulator layers, the layers ofinsulation may more easily be stripped and removed from the surface ofthe conductors. Therefore, after the stripping process, the flat cableis left having protruding conductors without any adhesive residue.Further, in a preferred embodiment, the stripped conductors do not haveany insulator residue either. Thus, it can be understood that thepresent invention provides for a flat cable having exposed conductorswhich do not have any residue which may inhibit the conductivity of theconductors and provide for a clean surface for the attachment of theconductors to a metallic surface and to allow for a successful solderingprocess where desired.

Furthermore, since the flat cable 10 does not use an adhesive to bondthe upper layer 20 to the lower layer 30, the flat cable 10 is lighterin weight than is a flat cable made using adhesives to bond theinsulating layers and conductors together. Testing has shown that when aflat cable having seven conductors, each conductor having across-section of 0.007 inches by 0.040 inches, was made havinginsulating layers of polyester each 0.0003 inches thick. The resultingflat cable weighed 43.5 grams for a ten foot length and the a flat cablemade with the same insulating materials and conductors and using anadhesive weighed 48.9 grams for a ten foot length. Thus, the sonicallywelded flat cable weighed 5.4 grams less for a ten foot length ascompared to the flat cable made using adhesive material. Therefore, fora seven conductor flat cable having polyester insulating layers the flatcable has a per unit length linear density of 4.35 grams/foot. The lowerweight of the flat cable 10 generally tends to increase the naturalfrequency of the flat cable 10. Thus, when the flat cable 10 isinstalled in a device such as a clockspring, the flat cable 10 is not assusceptible to low frequency vibrational energy often experienced inclocksprings. Therefore, the device which uses the flat cable 10 willtend to be more quiet than a device which does not use flat cable 10.

FIG. 5 is an alternate embodiment of the present invention showing theflat electrical cable 10 after the end portion has been stripped toexpose the conductors 40. The flat cable 10 shown in FIG. 1 disclosesthe cable 10 in its condition after the bonding procedure discussedabove. The cable 10 after the bonding procedure has the conductorsenclosed within the upper and lower insulator layers 20, 30. In order touse the flat cable 10 and enable it to be attached to a component, theconductors 40 must be exposed. As discussed above, the conductors may beexposed by stripping the cable to remove the upper and lower insulatorlayers at an end portion of the cable. As discussed above, proceduressuch as grinding or cutting the insulator layers with a knife may beused, in addition to the above procedure providing for nonbonded areas.FIG. 5 shows the flat cable 10 after a stripping procedure has beenapplied to the cable having the array of conductors 40 exposed at theend portion. The conductors 40 protrude from between the upper and lowerlayers 20, 30 of the insulator and are surrounded on the upper side ofthe conductor 40 by the rib 25 of the upper layer 20 and having seams 50on each side of the conductor 40. According to the advantages disclosedin the above invention, the conductors 40 do not have any adhesiveresidue thereon. After stripping of the end of the cable 10, no furtherprocedure such as a cleaning of the conductors is necessary. Due to thebonding method discussed above, without use of adhesives, the conductorsare clean and do not have residue which inhibits the conductivity of themetallic material. Following the stripping procedure and the exposure ofthe conductors 40 as shown in FIG. 5, the flat cable may then beattached to a component by soldering the array of conductors to aconnector or inserting the conductors into an electrical connector.Thus, it may be understood according to the above description that thepresent invention provides for a cable 10 which may be manufacturedquickly and easily and provide for a cost savings as well as providingfor a finished cable which may be more easily stripped and attached to acomponent. As an example, the component may be an electrical connectormounted to a housing of a clockspring.

In another embodiment, a perspective view of a preferred knurled flatcable 100 is shown in FIG. 7. The knurled flat cable 100 of FIG. 7 issimilar to the flat cable 10 of the embodiment discussed above, thedifferences between the two flat cables are discussed below. The upperlayer 120 is bonded to the lower layer 130 preferably by ultrasonicwelding using the plunging mode. The plunging direction 167 is shown inFIG. 6. FIG. 6 is a view of the horn 65 and anvil 70 assembly of FIG. 2where the rotary horn 65 operates in the plunge mode and the anvil is amodular rotary anvil 70 a. The modular rotary anvil 70 a is used toproduce the knurled flat cable 100, where the modular rotary anvil 70 ahas knurled protrusion 74 a, smooth broad protrusions 75, and smoothbroad edge protrusions 75 a. The knurled protrusions 74 a form theknurled surface texture pattern on the knurled seams 150 of the knurledflat cable 100. The smooth broad protrusions 75 and 75 a form the smoothcontinuous edge seams 115. The grooves 72 of the modular rotary anvil 70a form the raised surfaces or ribs 125. Conductors 140 comprise anintermediate layer between the upper layer 120 and the lower layer 130.An optical fiber 141 having at least one buffer coating is also shown inFIG. 7 in place of one of the conductors 140, as another embodiment ofthe invention. However, all of the conductors 140 could be replaced withfiber optic cables 141.

Experimental testing has shown that use of the plunge mode provides themost durable manufacturing method. Use of flat cable has shown that whenseams between adjacent conductors have a knurled surface texture pattern150 and the continuous edge seams 115 have a smooth continuous surfacetexture pattern such a flat cable is quiet in operation and provides forlow torque when installed in a clockspring. The knurled center seamsprovide a low amount of surface area contact when the tape contactsitself, thus reducing friction and hence torque, when in a clockspringthe flat cable is coiled up around itself. The smooth edge seam of theflat cable provides a smooth contacting surface between the flat cableand the interior surfaces of the clockspring housing and parts thereinsuch as damping material. Other embodiments were tested. No other formof flat cable performed as well. One test was conducted on a flat cablewhere all of the seams were knurled. Another test was conducted on aflat cable where all of the seams were smooth and continuous. Furthertesting compared flat cable bonded by the shear mode to flat cablebonded by the plunge mode of ultrasonic welding. Such durability isrequired when the knurled flat cable 100 is used in a clockspring. Flatcable used in a clockspring is coiled and held within the clockspringhousing where the flat cable is repeatedly partially uncoiled andrecoiled. However, since the flat cable is coiled, the flat cable mustbe flexible. A smooth edge seam is determined to be smooth relative tothe knurled seams located between adjacent conductors. As such, thesmooth edge seams have a surface roughness which is less than thesurface roughness of the knurled seams located between adjacentconductors.

In a preferred embodiment the knurled flat cable 100 is made with themodular rotary anvil 70 a as shown in FIG. 6. The anvil 70 a is called amodular rotary anvil since it is formed of discrete modular segments,sections, or inserts. FIGS. 8A and 9A display side views of twodifferent forms of the modular rotary anvil. FIG. 8A shows an assemblyof knurled inserts 160, broad protrusion inserts 162, a large bracketinsert 164, a small bracket insert 166, a first end segment 168, and asecond end segment 170 which form the modular rotary anvil 70 a. FIGS. 6and 8B shows the knurled insert 160 having recesses 72 and knurledprotrusions 74 a. FIGS. 10A through 13B display some of the variousindividual inserts.

FIG. 10A is a side view of the large bracket insert 164, and FIG. 10B isa front view of the large bracket insert 164. FIG. 11A is a side view ofthe small bracket insert 166, and FIG. 11B is a front view of the smallbracket insert. FIG. 12A is a side view of the knurled insert 160, andFIG. 12B is a front view of the knurled insert 160. FIG. 8B showsdetails of the knurled insert 160. FIG. 13A is a side view of the broadprotrusion insert 162, and FIG. 13B is a front view of the broadprotrusion insert 162. The assembly of inserts and segments are heldtogether with socket head cap screws. The socket head cap screws arecountersunk into one of the large bracket insert 164 and the smallbracket insert 166 and the socket head cap screws are threaded into oneof the other of the large bracket insert 164 and the small bracketinsert 166. The first end segment 168 is attached to the small bracketinsert 166 with socket head cap screws and the second end segment 170 isattached to the large bracket insert 164 with socket head cap screws.Alternatively, the assembly of inserts and segments are held together ona common shaft and secured with a nut and lock washer. The modularrotary anvil 70 a can then be mounted on the ultrasonic welding machineas would any conventional rotary anvil.

The modular rotary anvil 70 a can be used to make flat cable of manydifferent dimensions and configurations. As described above, in regardto the flat cable 10, a different rotary anvil 70 was required ifdifferent seam width dimensions were necessary. Thus, a manufacturer offlat cable would be required to maintain a large inventory of rotaryanvils. Such an inventory is expensive to produce and maintain.Furthermore, such an inventory relates directly to the cost of the flatcable produced. A further drawback to the rotary anvil concept is thatthe lag time between conception of a unique rotary anvil design and thefinished manufactured rotary anvil is a relatively long period of time.

Applicant's modular rotary anvil 70 a eliminates the need for a largeinventory of rotary anvils. Instead, now, a manufacturer need only keepan inventory of different modular segments, sections, or inserts. Theinserts can be built up or assembled in different ways to make a modularrotary anvil, where the modular rotary anvil produces a variety of flatcable designs. Such a concept supports flexible manufacturing needs,where the manufacture of different flat cable can be supported in ashort amount of time. Thus, meeting the needs of the market.Furthermore, the invention of the modular rotary anvil results in flatcable which costs less to produce as compared to the prior art.

FIG. 9A is a side view of another modular rotary anvil 70 b which hascutting inserts 172 interspersed between knurled inserts 160. FIG. 9B isa detailed view of a portion of FIG. 9A showing the cutting inserts 172.The cutting insert 172 attach to the modular rotary anvil 70 b the sameway as did the broad protrusion insert 162 of the modular rotary anvil70 a. In the embodiments discussed above the plurality of flat cablesproduced by a single rotary anvil were separated from each other by thecable splitter 89 shown in FIG. 4. The cutting insert 172 eliminates theneed for the cable splitter 89; thus, reducing the number of steps needto produce the flat cable. The cutting insert 172 achieves this resultby being able to ultrasonically bond the upper and lower layers togetherto form a seam, while substantially simultaneously the cutting insert172 cuts the flat cable of the just bonded seam. Other portions of themodular rotary anvil 70 b are the same as the modular rotary anvil 70 adescribed above.

In still yet another embodiment of the invention, a perspective view ofa preferred edge seam semi-knurled flat cable 200 is shown in FIG. 16.The edge seam semi-knurled flat cable 200 of FIG. 16 is similar to theknurled flat cable 100 of the embodiment discussed above and shown inFIG. 7, the differences between the two flat cables are discussed below.The upper layer 120 is bonded to the lower layer 130 preferably byultrasonic welding using the plunging mode. The operation of the plungemode is similar to that described in regard to the flat cable 100.However, in this embodiment, the modular rotary anvil would not have asmooth broad edge protrusion 75 a forming the smooth continuous edgeseam 115. Instead, the protrusion of the rotary modular anvil (notshown) has half of its width knurled and the other half smooth. Such aprotrusion of the rotary modular anvil forms a semi-knurled edge seam215. The semi-knurled edge seam 215 includes a first zone 217 adjacentone of the conductors which is knurled and a second zone 216 which issmooth, as shown in FIG. 16.

The semi-knurled edge seam flat cable 200 has the advantage that whenused in a clockspring, it is still quiet, due to the use of the smoothedge portion of the edge seam. However, this embodiment solves a problemby including the first zone 217 of the edge seam 215 which is knurled.The knurled seam requires less energy than the smooth continuous seam.Since the edge seam 215 includes a knurled zone, the edge seam 215requires less energy to bond the edge seam 215. The energy savings isthen directed towards the seams located between the conductors, so as tomake those seams 150 more strong. Otherwise, to ensure a proper bondbetween the upper layer 120 and the lower layer 130 at the location ofthe seams positioned between the conductors, the speed at which the flatcable exits the manufacturing machinery must be decreased. So thesemi-knurled edge seam 215 enables the flat cable 200 to exit themanufacturing machinery at a high rate of speed while still maintainingits structural integrity.

FIG. 17 is an expanded view of an alternative knurl or surface texturepattern as can be produced on flat cables 100 or 200. The raisedsurfaces or ribs 125 are smooth and the seam region 220, whichcorresponds to seams 150, can have a surface texture formed of a row ofrepeating parallel lines or linear segments, where the lines or linearsegments are substantially perpendicular to a length dimension of theflat cable. Such a surface texture is easy to grasp, forms a strongbond, and is a relatively easy pattern to impart on the modular rotaryanvil.

FIGS. 18–23 show end views of alternative conductors or conductorgroups. Alternative conductor configurations solve various problemsexperienced while using flat cable. A single conductor 140 isinexpensive to manufacture and assemble. Depending on the radius ofcurvature that the flat cable experiences, the conductor 140 mayexperience large bending stresses. As such, it is better to reduce thestresses by making the conductor smaller. Furthermore, a smallerconductor requires less force to bend the flat cable. Additionally,alternative conductor combinations make it possible to carry highercurrent loads for a short amount of time. FIG. 18 is an end view of asingle conductor 140 having a width, w, and a thickness, t, as shown inthe previous embodiments. FIG. 24 is an exploded, perspective view ofthe single flat conductor 140 assembled with an upper insulation layer120 and a lower insulation layer 130. The upper and lower insulationlayers 120, 130 are shown separated from each other for reasons ofclarity. The single conductor shown is just one of many that wouldpopulate the flat ribbon cable.

FIG. 19 is an end view of a dual or tandem conductor group 240, whereeach of the individual conductors 241, 242 are substantially identicalto each other. In this embodiment, each of the conductors 242, 241 has athickness, t, which is similar to that of the single conductor 140, anda width, w/2, which is substantially one-half of the width of the singleconductor 140. Thus, the dual or tandem conductor group 240 fits withinthe pre-existing space of the single flat conductor 140. Therefore, theshape of the rotary modular anvil does not change. FIG. 25 is anexploded, perspective view of the dual or tandem conductor group 240assembled with an upper insulation layer 120 and a lower insulationlayer 130. The dual or tandem conductor group shown is just one of manythat would populate the flat ribbon cable.

FIG. 20 is an end view of a dual stacked conductor group 243, where eachof the individual conductors 244, 245 are substantially identical toeach other. In this embodiment, each of the conductors 244, 245 has athickness, t/2, which is one-half of the thickness of the singleconductor 140, and has a width, w, which is similar to that of thesingle conductor 140. Thus, the dual stacked conductor group 243 fitswithin the pre-existing space of the single flat conductor 140.Therefore, the shape of the rotary modular anvil does not change. FIG.27 is an exploded, perspective view of the dual stacked conductor group243 assembled with an upper insulation layer 120 and a lower insulationlayer 130. The dual stacked conductor group shown is just one of manythat would populate the flat ribbon cable.

FIG. 21 is an end view of a triple stacked conductor group 246, whereeach of the individual conductors 247, 248, 249 are substantiallyidentical to each other. In this embodiment, each individual conductor247, 248, 249 has a thickness, t/3, which is substantially one-third ofthe thickness of the original conductor 140, and a width, w, which issimilar to that of the original conductor 140. Thus, the triple stackedconductor group 246 fits within the pre-existing space of the singleflat conductor 140. Therefore, the shape of the rotary modular anvildoes not change. FIG. 26 is an exploded, perspective view of the triplestacked conductor group 246 assembled with an upper insulation layer 120and a lower insulation layer 130. The triple stacked conductor groupshown is just one of many that would populate the flat ribbon cable.

FIG. 22 is an end view of a wire rope conductor group 250. FIG. 23 is anend view of a wire rope conductor 250 after the wire rope conductor 150has been compressed. Seven individual wires are shown. Each wire isapproximately 24 gauge. The compressed wire rope conductor 250 has athickness, t, similar to that of the original conductor 140, and awidth, w, similar to that of the original conductor 140. Thus, the wirerope conductor group 250 fits within the pre-existing space of thesingle flat conductor 140. Therefore, the shape of the rotary modularanvil does not change. FIG. 28 is an exploded, perspective view of thecompressed wire rope conductor group 250 assembled with an upperinsulation layer 120 and a lower insulation layer 130. The compressedwire rope conductor group shown is just one of many that would populatethe flat ribbon cable.

Furthermore, a single flat ribbon cable can include conductors ofvarious forms. As an example, a flat cable can have seven conductors.The first conductor can be a single flat conductor 140, the secondconductor can be a dual or tandem conductor 240, the third conductor canbe a dual stacked conductor 243, the fourth conductor can be a triplestack conductor 246, the fifth conductor can be a compressed wire ropeconductor 250, the sixth conductor can be an optical fiber 141, and theseventh conductor can be a single flat conductor 140. Other combinationsof conductors are possible and can be suited to the industrialrequirements of the use of the device.

Other embodiments are also envisioned such as a clockspring containingflat cable, where the clockspring connects crash sensors to an airbaglocated in a harness-type seat belt. Such a clockspring would take-upthe slack of the seat belt when the seat belt spooled and un-spooled.Non-automotive applications are also envisioned.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications may be madewithout departing from the spirit and scope of the present invention andwithout diminishing its attendant advantages. It is, therefore, intendedthat such changes and modifications be covered by the appended claims.

1. A method of assembling a flat electrical cable comprising the stepsof: simultaneously feeding an upper and lower layer of insulatingmaterial and an intermediate layer of conductors between a horn and amodular rotary anvil; ultrasonically bonding the upper and lower layerstogether along a seam substantially parallel and adjacent theconductors, and applying a textured pattern to the lower layer thatextends flatly and continuously along substantially the entire outersurface of the lower layer providing a friction reducing surface on thelower layer to reduce friction between the lower layer and anothersurface.
 2. The method of claim 1 wherein the step of ultrasonicallybonding includes the horn operating in a plunge mode.
 3. The method ofclaim 1 wherein the step of simultaneously feeding includes the modularrotary anvil having at least one segment having a series of grooves andprotrusions corresponding to the arrangement of the conductors orientedbetween the insulator layers wherein the insulator layers are compressedbetween the protruding portion and a weld surface of the rotary horn inorder to form the seams.
 4. The method of claim 3 wherein at least oneof the protrusions of the modular rotary horn has a textured surfacepattern.
 5. The method of claim 4 wherein the textured surface patternis a knurled surface pattern.
 6. The method of claim 3 wherein at leastone of the protrusions of the modular rotary anvil has a smooth surfacepattern.
 7. The method of claim 1, further comprising the steps ofcutting the flat cable into individual lengths and stripping ends of theflat cable.
 8. The method of claim 7 wherein the step of strippingincludes the sub-steps of removing the upper and lower insulator layersso as to leave the conductors exposed and protruding beyond the end ofthe flat cable.
 9. The method of claim 7 wherein the step of strippingincludes the sub-step of inserting the end of the flat cable into arotary grinding machine to remove the upper and lower insulator layersto expose a width of the conductors, and removing the excess end portionof the cable to leave the protruding conductors.
 10. The method of claim1, further comprising the step of testing the assembled flat cable forthe presence of bonded seams.
 11. The method of claim 1 wherein the stepof simultaneously feeding the intermediate layer of conductors includesat least one conductor which is a fiber optic cable.
 12. The method ofclaim 1, further comprising the step of: inserting the flat cable into ahousing.
 13. The method of claim 1, further comprising the steps of:stripping a first end of the flat cable so as to expose the conductors,and further comprising the step of attaching an electrical connector tothe first end of the flat cable, and wherein the electrical connector ismounted to the housing, and wherein the step of attaching immediatelyfollows the step of stripping.